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Trinity College Dublin

Introduction to Microscopy

Traditionally the wavelength of light has limited the imaging resolution of optical microscopes to approximately 200 nm. This is about 1,000 atoms across, or 1 metre divided 5 million times! Using finely focused beams of charged particles such as electrons, with much shorter wavelengths than light, sub atomic resolution imaging is now possible.

Transmission electron microscopy [TEM] is similar to the traditional light microscope. An electron beam is sent through a very thin specimen. The resolution limit is less than 1 tenth of a nanometre. Scanning electron microscopy [SEM], visualizes details on the surfaces of specimens to approx. 1 nm imaging resolution. Electron microscopes equipped for X-ray spectroscopy, or more advanced analytic techniques can provide qualitative and quantitative elemental analysis. Ion microscopes, using finely focused beam of charged particles such as gallium or helium are used for high resolution imaging and patterning, similar to an atomic chisel.

Transmission electron image of a single Silicon nanowire, from the group of Prof. Mick Morris, CRANN/UCC, whose team use microscopy to investigate materials for reducing component sizes on personal computers, and for energy storage applications.

The ability to image, understand, and manipulate materials on shorter length-scales is important in a huge range of research disciplines, from Physics, Chemistry, Biology, Medicine, Engineering and Natural Sciences. Microscopy is also critical to the development of new products and process improvements. For example latest transistors being developed by PC manufacturers are now only 100 atoms wide…